Merchandise displays, particularly for small articles, have developed into hook or peg supported cards upon which the merchandise is individually mounted. Many such displays are for self-service but since the cards and the merchandise are relatively small they lend themselves to shoplifting; and it is the object of the present invention to provide a relatively simple device for avoiding such shoplifting and making it necessary, in order to remove any of the merchandise, to unlock it so that the cards are released and may be removed.